A wide variety of automated diagnostic instruments (e.g., chemical analyzers or immunoassay instruments) are used to analyze patient specimens. These diagnostic instruments may conduct assays or testing using one or more reagent or other additions to identify one or more analytes in, or characteristics of, a biological liquid such as urine, blood serum or plasma, cerebrospinal liquids, and the like (hereinafter “bio-liquid”). For convenience and safety reasons, these bio-liquids may be contained within sample containers (e.g., sample tubes).
For certain tests, the patient specimen may include a serum or plasma portion (obtained from whole blood by centrifugation). To prevent clotting, an anticoagulant such as citrate or heparin may be added to the patient specimen. After centrifuging and subsequent de-capping, the open sample container (e.g., sample tube) may be transported to, or otherwise reside in, a support article, such as a sample rack.
The sample rack may be accessible by a pipette of an aspirating system that may extract bio-liquid from the sample container and combine the bio-liquid with one or more reagents and possibly a diluent in a reaction container (e.g., cuvette or cup). After incubation or reaction, analytical measurements may then be performed, using, for example, photometric or fluorometric readings, or the like. The measurements allow determination of values from which an amount of analyte or other substance related to the health of the patient may be determined using well-known techniques.
In some cases, improper addition of amounts of specimen, other liquids, and/or liquid or solid reagents may affect the integrity of the testing results, such as the analyte reading of a clinical analyzer. Verification of the aspiration amount of the patient specimen may have been accomplished by recording and monitoring aspiration pressure readings in prior systems. However, this method may be problematic in some instances, especially at low volumes. Verification of liquid reagent addition and diluent may suffer from similar problems. Solid reagent addition may not be verified using existing methods.
Because of the problems encountered due to improper addition amounts of specimen, reagent, and/or liquid or diluent addition, there is an unmet need for methods and apparatus adapted to measure and/or verify such additions in clinical testing.